Hand held tool for facilitating removal and installation of a return spring and rollers in an S-cam type drum brake assembly

ABSTRACT

A hand held tool for maintaining an S-cam drum brake assembly includes an elongated middle portion and a first end which is adapted for facilitating removal and installation of the return spring. A notch is provided in the first end for receiving a rigid rod of the return spring and for enabling a surface of the first end to abut an end of one coil of the return spring when the first end is inserted through the pair of the spaced ribs in a brake shoe. An offset portion is formed intermediate the middle portion and the first end of the tool for positioning it for engagement with the coil of the return spring when at least one of the rollers is removed from the drum brake assembly and when the middle portion of the tool abuts an end of the S-cam. An opposed second end of the tool is adapted for facilitating removal and installation of rollers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority from U.S. Provisional Patent Application Ser. No. 60/762,693 filed on Jan. 27, 2006.

FIELD OF THE INVENTION

The present invention relates, in general, to hand held tools and, more particularly, this invention relates to a hand held tool for facilitating removal and installation of a return spring and rollers employed in an S-cam type drum brake assembly.

BACKGROUND OF THE INVENTION

Drum brake assemblies for a wheel mounted on an axle of a heavy duty truck or a bus are well known in the art. They generally include a drum which is mounted on the axle. A pair of brake shoes are operatively positioned within the drum. Each brake shoe has a lining which is secured to a curved flange having a pair of spaced ribs and an anchor pin extending therebetween and secured thereto. There is a cam shaft which is mounted in a fixed position relative to the axle and an S-cam being rigidly attached to one end of the cam shaft for rotation therewith. A roller is journalled within a notched end of each brake shoe positioned adjacent the S-cam and contacts an outer surface of the S-cam. During brake application, the rotation of the cam shaft and the S-cam causes each roller to rise on the outer surface of the S-cam and expand brake shoes outwardly for contacting the liners with inner surfaces of the drum. A return spring means is provided to return the brake shoes to their original non-actuated position. The spring means has a rigid rod and a pair of coils each mounted at a respective end of the rod and releaseably secured onto a respective anchor pin with the end hook. The coils are stretched at assembly to provide a restraining force on the brake shoes away from the drum and to maintain the rollers in a continuous contact with the S-shaped cam.

As is generally well known, difficulties arise in removing and replacing the brake shoes during servicing of the installed drum brake assemblies due to the tension in the return spring coils and limited clearances around various brake components. Furthermore, it has been found that the use of conventional screwdrivers, pry bars and other hand held tools provides for less than desirable level of safety during return spring removal and installation process.

Efforts have been made to improve removal and replacement of the brake shoes. U.S. Pat. No. 5,507,803 issued to Redgrave et al discloses a generally straight elongated lever tool which is insertable through the notch between the ribs in the end of a brake shoe. A notch in the end of the tool engages the rod between the coils of the return spring when the tool is inserted between the brake shoe ribs at the end of the brake shoe. The tool is fulcrummed about the end of the brake actuating S-cam or roller for stretching the spring. One side of the notched end of the tool is concave or cupped to contact one of the return spring coils for direct axial lift or stretch to cause the spring end hook to snap over an anchor pin up installation. The opposite side of the notched end of the tool surface is inclined for return spring removal such that upon reversed insertion of the tool with the inclined surface against the spring coil and fulcrumming about the S-cam or roller, the coil is deflected laterally upon stretching of the return spring to cause the end hook to clear the anchor pin upon relaxation of the return spring. One disadvantage of this prior art tool is in the need to use different surfaces of the notched end for removal and installation of the return spring. Another disadvantage of this prior art tool is in its configuration to remove and install return spring with the rollers positioned within the notched end of the brake shoes and abutting the opposed surfaces of the S- cam and thus forming higher than desirable tension in the return spring coils. There is a need for an improved tool for facilitating removal and installation of the return spring in the heavy duty drum brake assembly.

SUMMARY OF THE INVENTION

According to the first embodiment, the present invention provides a unitary hand held tool for maintaining a drum brake assembly for a wheel mounted on an axle. The drum brake assembly includes a drum and a pair of expending brake shoes each having a lining being secured to a curved flange having a pair of spaced ribs and an anchor pin extending therebetween and secured thereto. A cam shaft is mounted in a fixed position relative to the axle. An S-cam is rigidly attached to one end of the cam shaft for rotation therewith. A pair of rollers are provided, wherein each roller is journalled within a notched end of the brake shoe positioned adjacent the S-cam and contacting a side of the S-cam. A return spring means has a rigid rod and a pair of coils each mounted at a respective end of the rod and releaseably secured onto a respective anchor pin. The coils are stretched at assembly to provide a restraining force on the brake shoes away from the drum and to maintain the rollers in the end of the brake shoes in contact with the S-shaped cam. The tool includes an elongated generally straight middle portion. A first end is provided for facilitating removal and installation of the return spring means. A notch is formed in the first end for receiving the rigid rod and for enabling a surface of the first end to abut an end of one coil when the first end is inserted through the pair of the spaced ribs. An offset portion is formed intermediate the middle portion and the first end for positioning the first end of the tool for engagement with the coil of the return spring means when at least one of rollers is removed from the drum brake assembly and when the middle portion abuts and fulcrums about an end of the S-cam. An opposed second end is provided, whereby a first force which is applied in a first direction to the second end fulcrums the tool about the end of the S-cam for selectively releasing from and securing the coil to the anchor pin.

According to a second embodiment of the invention, therein is provided a method of removing a return spring in a drum brake assembly for a wheel mounted on an axle. The drum brake assembly includes a drum and a pair of expending brake shoes each having a lining being secured to a curved flange having a pair of spaced ribs and an anchor pin extending therebetween and secured thereto. A cam shaft is mounted in a fixed position relative to the axle. An S-cam is rigidly attached to one end of the cam shaft for rotation therewith. A pair of rollers are provided with each roller being journalled within a notched end of the brake shoe positioned adjacent the S-cam and contacting a side of the S-cam. A return spring has a rigid rod and a pair of coils each mounted at a respective end of the rod and releaseably secured onto a respective anchor pin. The coils are stretched at assembly to provide a restraining force on the brake shoes away from the drum and to maintain the rollers in the end of the brake shoes in contact with the S-shaped cam. The method includes the step of providing an elongated generally straight tool having a first notched end and a generally flat second end. Then, positioning a generally flat second end through a pair of spaced ribs in one of the pair of shoes for abutment with a respective anchor pin. Next, applying a first force in a first direction to a first end of the tool. Moving a notched end of the one brake shoe in a direction away from the S-cam. Then, removing a roller jornalled in the notched end being moved away. Next, releasing the first force to return the notched end being moved away towards the S-cam. Extracting the second end of the tool from the drum brake assembly. Next, positioning the first notched end of the tool through the pair of spaced ribs in the one shoe for abutment with one end of a respectively positioned coil. Then, applying a second force in a second direction at the second end to fulcrum the first notched end of the tool about an end of the S-cam. Finally, releasing an opposed end of the respectively positioned coil from engagement with the anchor pin.

OBJECTS OF THE INVENTION

It is, therefore, one of the primary objects of the present invention to provide a hand held tool for removing and installing a return spring in a heavy duty drum brake assembly.

Another object of the present invention is to provide a return spring removal and installation hand held tool which is configured for use with the minimum amount of tension formed within such return spring.

Yet another object of the present invention is to provide a return spring removal and installation hand held tool which is economical to manufacture.

A further object of the present invention is to provide a return spring removal and installation hand held tool which is suitable for removal and installation of rollers employed in the drum brake assembly.

Yet a further object of the present invention is to provide a return spring removal and installation hand held tool which enhances operational safety.

In addition to the several objects and advantages of the present invention which have been described with some degree of specificity above, various other objects and advantages of the invention will become more readily apparent to those persons who are skilled in the relevant art, particularly, when such description is taken in conjunction with the attached drawing Figures and with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a hand held tool of the present invention for facilitating removal and installation of a return spring and rollers employed in an S-cam type drum brake assembly;

FIG. 2 is a planar view of the hand held tool of FIG. 1;

FIG. 3 is a side elevation view of an S-cam type drum brake assembly, particularly showing the hand held tool of the present invention positioned for removing and installing the rollers; and

FIG. 4 is a side elevation view of an S-cam type drum brake assembly, particularly showing the hand held tool of the present invention positioned for removing and installing the return spring.

BRIEF DESCRIPTION OF THE VARIOUS EMBODIMENTS OF THE INVENTION

Prior to proceeding to the more detailed description of the present invention, it should be noted that, for the sake of clarity and understanding, identical components which have identical functions have been identified with identical reference numerals throughout the several views illustrated in the drawing figures.

Reference is now made to FIGS. 3-4, wherein there is shown a drum brake assembly, generally designated 10, which is mountable onto a wheel axle (not shown) of a heavy duty truck or a passenger bus. Such drum brake assembly 10 is well known in the art. Briefly, the drum brake assembly 10 includes a drum 12 which is partially illustrated and which has an inner surface 14. A pair of brake shoes, generally designated as 20, are operatively positioned within the drum 12. Each brake shoe 20 has a lining 22 which is secured to a curved flange 24 having a pair of spaced ribs 26 and an anchor pin 28 which extends therebetween and secured thereto. There is a cam shaft 30 which is mounted in a fixed position relative to the axle and an S-cam 32 being rigidly attached to one end of the cam shaft 30 for rotation therewith. A roller 36 is journalled within a notched end 29 of each brake shoe 20 which is positioned adjacent the S-cam 32 and contacts an outer surfaces 33, 34 of the S-cam 32. During brake application, the rotation of the cam shaft 30 and the S-cam 32 causes each roller 36 to rise on the outer surface 33, 34 of the S-cam 32 and expand brake shoes 20 outwardly for contacting the lining 22 with the inner surface 14 of the drum 12. A return spring means, generally designated as 40, is provided to return the brake shoes 20 to their original non-actuated position during brake release. The spring means 40 has a rigid rod 42 and a pair of coils 44 each mounted at a respective end of the rod 42 and releaseably secured onto a respective anchor pin with 28 the end hook 46. The coils 44 are stretched at assembly to provide a restraining force on the brake shoes 20 away from the inner surface 14 of the drum 12 and to maintain the rollers 36 in the end of the brake shoes 20 in continuous contact with the S-cam 32. Additional details of the drum brake assembly 10 which are relevant to the present invention are disclosed in U.S. Pat. No. 5,507,083 whose teachings are incorporated into this document by reference thereto.

Now in reference to FIGS. 1-2, a unitary hand held tool, generally designated as 50, for facilitating removal and installation of the return spring 40 and rollers 36 includes an elongated generally straight middle portion 52 which has each of a predetermined length, a predetermined cross-section and a predetermined rigidity. The middle portion 52 of the tool 50 has a presently preferred round cross-section having a diameter of about 0.5 inches. An offset portion 54 is formed at one end of the middle portion 52 and in a direction of a longitudinal axis 53 of such elongated middle portion 52. Furthermore, such offset portion 54 is formed at an angle of about 45 degrees to the longitudinal axis 53 of the middle portion 52. It has been determined that the height H of such offset portion 54 being about 1.25 inches provides for desirable positioning of the first end 56 within the drum brake assembly 10.

A first end 56 of the tool 50 terminates the distal end of the offset portion 54 and is provided for facilitating removal and installation of the return spring means 40. The first end has a first surface 58 which is oriented towards the middle portion 52 and an opposed second surface 60. The surfaces 58 and 60 are joined with an outer edge 62. The presently preferred shape of at least the first surface 58 is concaved, however the present invention contemplates that such first surface 58 may be cup-shaped. It is further preferred for the second surface 60 to have a shape which is generally identical to the shape of the first surface 58. The thickness of the first end 56 progressively increases from the outer edge 62 thereof to the offset portion 54 to negotiate available clearances within the drum brake assembly 10 during use. The presently preferred thickness of the first end 56 at the outer edge 62 is about 0.06 inches. It is further preferred that the thickness of the offset portion 54 continuously increases from the first end 56 to the juncture with the middle portion 52.

A U-shaped notch 64 is formed in the first end 56 and, more particularly in the outer edge 62, for receiving the rigid rod 42 and for enabling the first surface 58 to abut an end of one coil 44 when the first end 56 of the tool 50 is inserted through the pair of spaced ribs 26.

An opposed second end 66 of the tool 50 is adapted for facilitating removal and installation of rollers 36 and has each of a predetermined shape and a predetermined thickness. Such second end 66 may be generally flat and preferably has a thickness which progressively increases from the outer edge 68 thereof to the juncture with the middle portion 52. Furthermore, the width of the second end 66 is determined based on the spacing between the ribs 26 and to provide for sufficient leverage about the anchor pin 28.

The presently preferred overall length of the tool 50 is about 16.0 inches.

It has been found that in order to reduce the effort required to remove return spring means 40 it is advantageous to first reduce the tension formed in each coil 44. Accordingly, the method of removing the return spring means 40 contemplates first using the second end 66 of the tool 50 to remove at least one roller 36. Specifically, the method includes the step of positioning the second end 66 through the pair of spaced ribs 26 in one of the curved flange 22 of the brake shoe 20 for abutment with a respective anchor pin 28, as best shown in FIG. 3. Then, applying a first manual force in a first direction at a first end 56 of the tool 50. Next, moving a notched end 29 of the brake shoe 20 in a direction away from the S-cam 32. Then, manually removing the roller 36 which is journalled in the notched end 29. Next, releasing the first manual force to return the notched end 29 towards the S-cam 32. The first direction of the first manual force depends on the position of the roller 36 to be removed. For exampled, if the upper roller 36 is to be removed, as shown in FIG. 3, then the first manual force will be applied in an upward direction. After the roller 36 is removed, the second end 66 is extracted from the drum brake assembly 10 and rotated 180 degree to orient the first end 56 towards the drum brake assembly 10. The method further includes the step of positioning the first end 56 through the pair of spaced ribs 26 of the brake shoe 20 having the roller 36 removed therefrom for abutment with one end of a respectively positioned coil 44, as best shown in FIG. 4. Then, applying a second manual force in a second direction at the second end 66 to fulcrum the first end 56 of the tool 50 about an end 33 of the S-cam 32. Finally, releasing an opposed end of the respectively positioned coil 44 from engagement with the anchor pin 28. The second direction of the second manual force will depend on the coil 44 to be engaged. Such second manual force will be applied in a downward direction if an upper coil 44 is to be removed in FIG. 4. It has been found that a second manual force of about 5 pounds to about 7 pounds is sufficient to remove or install return spring means 40 when both rollers 36 have been removed. The employment of the offset portion 54 of the present invention simply and easily positions the first end 56 for engagement with the end of the coil 44 when such at least one roller 36 is removed from the drum brake assembly 10 and when the middle portion 52 adjacent the offset portion 54 abuts and fulcrums about the end 33 of the S-cam 32. The return spring means 40 may be simply removed from the drum brake assembly 10 if required by simply unhooking the second coil 44 from the second anchor pin (not shown).

The method further contemplates the step of removing the second roller 36 prior to removal of the return spring means 40 in order to reduce the tension in coils 44 to its absolute minimum.

The installation of the return spring means 40 and rollers 36 is achieved in the reversed order and will not be described for the sake of brevity.

The presently preferred material of the unitary tool 50 is metal and more preferably, alloyed steel such as molybdenum-vanadium steel, which is well known as a material for manufacturing high quality screwdrivers and other hand held tools. Furthermore, at least a portion of such tool 50, for example ends 56 and 66 may be tempered to increase the life of the tool 50. Alternatively, other materials having a rigidity which is sufficient for removal and installation of the return spring means 40 and rollers 36 may be employed in the present invention.

Although the present invention has been shown in terms of the width of middle portion being less than a width of each of the first end and the second end, it will be apparent to those skilled in the art, that the present invention may be applied to the tool 50 having a uniform width throughout.

Thus, the present invention has been described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same. It will be understood that variations, modifications, equivalents and substitutions for components of the specifically described embodiments of the invention may be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims. 

1. A unitary hand held tool for maintaining a drum brake assembly for a wheel mounted on an axle, said drum brake assembly including a drum, a pair of expending brake shoes each having a lining being secured to a curved flange having a pair of spaced ribs and an anchor pin extending therebetween and secured thereto, a cam shaft mounted in a fixed position relative to the axle, an S-cam being rigidly attached to one end of the cam shaft for rotation therewith, a pair of rollers each journalled within a notched end of the brake shoe positioned adjacent the S-cam and contacting an outer surface of the S-cam, a return spring means having a rigid rod and a pair of coils each mounted at a respective end of the rod and releaseably secured onto a respective anchor pin, wherein the coils are stretched at assembly to provide a restraining force on the brake shoes away from the drum and to maintain the rollers in continuous contact with the S-shaped cam, said tool comprising: (a) an elongated generally straight middle portion; (b) a first end for facilitating removal and installation of the return spring means; (c) a notch formed in said first end for receiving the rigid rod and for enabling a surface of said first end which is oriented towards said middle portion to abut an end of one coil when said first end is inserted through the pair of the spaced ribs; (d) an offset portion which is formed intermediate said middle portion and said first end and which extends in a direction of a longitudinal axis of said middle portion for positioning said first end of said tool for engagement with one coil of the return spring means when at least one of the pair of rollers is removed from the drum brake assembly and when said tool abuts and fulcrums about an end of the S-cam; (e) an opposed second end; and (f) whereby a first manual force applied in a first direction to said second end fulcrums said tool about the end of the S-cam for selectively releasing from and securing the coil to the anchor pin.
 2. The tool, according to claim 1, wherein said opposed second end is generally flat for facilitating removal and installation of the rollers, and wherein said second end is insertable through the pair of the spaced ribs in each of such pair of brake shoes for abutting the anchor pin, whereby a second manual force applied in a second direction to said first end of said tool moves the notched end of the brake shoe in a direction away from the S-cam for selectively removing from and installing the roller within the notch end.
 3. The tool, according to claim 1, wherein a thickness of said first end progressively increases from an outer edge thereof to a beginning of said offset portion.
 4. The tool, according to claim 1, wherein said tool includes a uniform width throughout.
 5. The tool, according to claim 1, wherein a width of said middle portion is less than a width of each of said first end and said second end.
 6. The tool, according to claim 1, wherein said offset portion is formed at an angle of about 45 degrees to said longitudinal axis of said middle portion.
 7. The tool, according to claim 1, wherein a material of said tool is a metal.
 8. The tool, according to claim 7, wherein said metal is alloyed steel.
 9. The tool, according to claim 1, wherein said first end is one of a concave and cup-shaped.
 10. The tool, according to claim 1, wherein a thickness of said second end progressively increases from an outer edge thereof to a beginning of said middle portion.
 11. The tool, according to claim 1, wherein said offset portion is capable of positioning said first end of said tool for engagement with one coil of the return spring means when both rollers are removed from the drum brake assembly and when said tool abuts and fulcrums about the end of the S-cam.
 12. A method of removing a return spring means in a drum brake assembly for a wheel mounted on an axle, said drum brake assembly including a drum, a pair of expending brake shoes each having a lining being secured to a curved flange having a pair of spaced ribs and an anchor pin extending therebetween and secured thereto, a cam shaft mounted in a fixed position relative to said axle, an S-cam being rigidly attached to one end of said cam shaft for rotation thererewith, a pair of rollers each journalled within a notched end of each of said pair of brake shoes positioned adjacent said S-cam and contacting an outer surface of said S-cam, a return spring means having a rigid rod and a pair of coils each mounted at a respective end of said rod and releaseably secured onto a respective anchor pin, wherein said coils are stretched at assembly to provide a restraining force on said brake shoes away from said drum and to maintain said rollers in continuous contact with said S-shaped cam, said method comprising the steps of: (a) providing an elongated generally straight hand held tool having a first notched end and a generally flat second end; (b) positioning said generally flat second end through said pair of spaced ribs in one of said pair of brake shoes for abutment with a respective anchor pin; (c) applying a first manual force in a first direction to said first notched end of said tool; (d) moving a notched end of said one brake shoe in a direction away from said S-cam; (e) removing a roller jornalled in said notched end being moved away in step (d); (f) releasing said first manual force applied in step (c); (g) returning said notched end being moved away in step (d) towards said S-cam; (h) extracting said second end of said tool from said drum brake assembly; (i) positioning said first notched end of said tool through said pair of spaced ribs in said one brake shoe having said roller removed from for abutment with one end of a respectively positioned coil; (j) applying a second manual force in a second direction to said second end; (k) fulcruming said first notched end of said tool about an end of said S-cam; and (l) releasing an opposed end of said respectively positioned coil from engagement with said anchor pin.
 13. The method, according to claim 12, wherein said method includes the step of repeating steps (b) through (h) to remove a second roller prior to positioning said first notched end of said tool in step (i). 